Torpedo control apparatus



Sept. l5, 1954 J. H. RAY

' ToRPEDo CONTROL APPARATUS 2 Sheets-Sheet l Filed Oct. 5l, 1960 I l I lI I l l 4 555mm IW wm Q5,

INVENTOR. JULIAN H. RAY

ATTORNEY.

States ate Unite i This invention relates to guidance and controlapparatus for naval torpedoes and more particularly to apparatus of thetype wherein intelligence is communicated between the torpedo and aremote station through an extensible conductor connecting same,sometimes called wire guided torpedo apparatus.

While evidence is available that the broad concept of guiding a torpedoby electric signals transmitted through an extensible conductorconnecting the torpedo and a control station is old, probably havingoriginated in a foreign country, such concept was ostensibly employedwith direct current communicating techniques and, so far as known, thecontrol station was stationary.

In accordance with generally know principles, D.C. cornmunicationtechniques are somewhat limited in their capability to provide aplurality of communication channels and also limited in their capabilityto provide two-way communication. It has been found that theselimitations can be obviated using the principles and apparatus to besubsequently described.

The principal object of the present invention is to provide wire guidedtorpedo apparatus capable of simultaneously controlling a greater numberof torpedo control functions than heretofore possible, and capable ofsimultaneously telemetering torpedo performance data from the torpedo tothe remote station.

Other objects and many of the attendant advantages of this inventionwill be readily appreciated as the same becomes better understood byreference to the following detailed description in connection with theaccompanying drawings wherein:

FIG. 1 is a schematic diagram of one form of the torpedo apparatus ofthe present invention;

FIGS. 2 and 3 are details of FIG. l;

FIG. 4 is a block diagram of another form of invention; and

FIG. 5 is a block diagram of a still further form of invention.

Referring now to FIG. l of the drawing, the invention comprises, ingeneral, wire guided torpedo apparatus which may be employed in varioustactical organizations wherein a torpedo is to be controlled from aremote guidance locus, such as a ship, submarine, harbor defensestation, hovering aerial vehicle, iioating buoy linked by radio relayapparatus to another station or the like, one of which is illustrated inFIG. l as a torpedo it) to be guided from a guidance station 12 aboard aship 14.

Housed in the torpedo is apparatus for dispensing wire as the torpedoinns through the water, of any suitable form, but preferably ashereinafter described and shown in FGS. 1 and 2, comprising a dispenserhousing 16a containing a stationary coil of wire 18a which at the startof the run has a length equal to the range of the torpedo. The wire is asingle conductor wire having an insulation thereabout, which insulationis preferably of a type exhibiting a combination of a low dielectricconstant in seawater which is uniform over the audio frequency range,and abrasion resistant. By way of illustration, satisfactory results maybe obtained using No. 24 hard drawn copper wire as the conductor and aninsulation comprising a polyethylene inner sheath 11 mils thick toprovide the desired dielectric characteristics tending to lower theshunt distributed capacity between the conductor and the seawatermedium, and a nylon outer sheath 5.5 mils thick to provide the requisiteresistance and strength. Polyethylene has a dielectric constant equal to3.3 and nylon has a dielectric equal to 6.0. Coil 13a is formed as aconventional multilayer helical coil, having an axial hollow coreextending therethrough, with one end of the length of wire appearing atthe innermost coil layer adjacent the core and the other end appearingat the outermost layer. Further, the coil is so wound, as by applicationof twist in forming each coil turn and application of a suitable lightadhesive to prevent tangling, that the end appearing at the innermostlayer may be freely and easily uncoiled and pulled from the core by aslight pull in an axial direction. This end is threaded through a guidetube Ztl and then extends into the seawater medium between the torpedoand ship, and the other end is passed through a gland in the housing loainto the torpedo. Housing 16a is flooded with seawater admitted thereinthrough a venting arrangement and the coil is mounted in the housing inspaced relationship relative to the housing Wall to provide fullimmersion of the coil in the seawater. A like housing lob and like coillSb may be carried by ship lli with the housing suitablyfilled withseawater and with the freely uncoilable end extending into the seawatermedium.

The uncoiled ends of coils 18a and 1gb are joined together by a suitablewater-tight splice, not shown, so that the wire of coils 13a and lb ineffect constitute a continuous wire ES with a midportion lim extendingthrough the seawater medium between the ship and torpedo. Shortly afterstart of the torpedo run a reactive or resistive force comprisinginertia and friction forces associated with midportion lltlm overcomesthe tendency for relative movement between the torpedo and ship to pullthe wire through the water. Thereafter the reactive force pulls wirefrom each coil under relative movement between the respective coil andthe midportion 18m. It will be apparent that with such arrangement thetension in midportion l3nt never exceeds the force necessary to uncoiland pull the wire from the coils and that such arrangement permits boththe torpedo and the ship to maneuver at will. Both the torpedo and shipin etfect run away from the stationary wire midportion 18m dispensingwire into the sea to extend the length of the midportion.

In order to communicate signals for controlling the torpedos azimuthcourse and depth course from guidance station l2 to the torpedo there isprovided an A.C. signal transmitting unit 22 comprising a series of fourxed frequency audio frequency oscillators 24a, 24h, 24C, 24d forproducing A.C. sine wave electrical energy characterized by separatefrequencies of operation. Oscillators 24a and Zeb form a pair to providecommand signals for left and right course changes, respectively. A`suitable keying arrangement 26 is provided to selectively produce asignal output in the form of an A.C. pulse from one or the other of theoscillators. Similarly, oscillators 24e and 24d, having a similar keyingarrangement 26a, are paired to provide up and down depth change signals.These signal outputs are fed to a conventional mixer 2S which combinesthem into a single resultant signal of AC. electrical energy having asfrequency components the frequencies of the inputs, permittingsimultaneous transmission of azimuth and depth change signals. Theoutput of the mixer is then fed through a power amplifier to a matchingtransformer 30, and the transformer output winding together with aparallel resistor Mia, are connected between the shipboard end of wire18 and a seawater ground. Wire 18 forms one conducting path and theconductivity of the seawater medium between the ship and torpedo formsanother conducting path of a transmission line extending between theship and torpedo which conducts the signal from the ship to the torpedoWhere it appears across a capacitor and resistor network 31 which isconnected between the torpedo end of wire f8 and a seawater ground.Together, dispenser housing 16a, -16b, wire coils lltia, 18h, Wiremidportion 18m, and the aforesaid seawater ground return networks in theship and torpedo, form wire dispensing and communication circuitapparatus 32. Network 31 also forms the input of an amplifier 33. it isa characteristic that the attenuation loss across apparatus 32 increasesduring the torpedo run, causing the level lof signal at amplifier 33 tovary. If desired amplifier 33 may be of the automatic volume controltype having in combination therewith suitable circuitry for controllingits amplification in accordance with the level of input signal, andthere may be provided an additional oscillator 34 at the shipboardstation to provide a separate and distinct continuous signal to be fedto mixer 23, to be passed over the transmission line to operate theamplification control circuit, maintaining the amplier output withindesired limits. The output of ampliiierfi is passed to the inputsolenoid 35 of conventional resonant reed relay apparatus 35 forseparating the resultant AC. signal into its component frequency signalsand converting them to a D.C. output. Apparatus 36 has a series of fourfrequency selective relays 33a, 38h, 33C, 38d. Each relay has avibrating reed element magnetically coupled to the magnetic iield ofsolenoid 35 and tuned to physically vibrate when a predeterminedfrequency component is present in the input to solenoid 35. By means ofa suitable pulse forming network, including an R-C network, thevibration is converted to a DC. output. Relays Stia, Sb, etc. are tunedto operate at frequencies corresponding to those of the series ofoscillator 24a, 2s/tb, etc., with the oscillator and the relay havingthe same suffix letter constituting a matched set for transmitting andreceiving. When the oscillator of a set is keyed to provide a pulsesignal its matching reed relay receives the signal and produces a D.C.output pulse. The frequencies allocated to the oscillator and reed relaysets are from a series of frequencies chosen to avoid cross interferenceby harmonics and other modulation products to permit simultaneousoperation of the matched sets so that each matched set provides aseparate and distinct frequency channel of communication. By way ofillustration, satisfactory results may be obtained by allocation offrequencies from the series consisting of 289 c.p.s., 357 c.p`.s., 234c.p.s. and 189 c.p.s. as shown in the drawing. As will be apparent,additional matched sets of oscillators and reed relays may be employedto provide additional channels of communication to control other torpedocontrol functions such as the enabling of the warhead, illustration ofwhich has been omitted in the interests of clarity.

In the torpedo there is provided an azimuth steering control channelresponsive to the D.C. pulse signals produced at the output of frequencyselective relays 38a and 38h, of any suitable form, but preferably ashereinafter described. The outputs of relay 33a and Sib are fed to firstand second input solenoids 3%, 39h which actuate the ratchets of acombination electromagnet and ratchet mechanism 40a having a ratchetwheel which is rotated through a small angular step in either ofopposite directions of rotation depending upon which of the inputsolenoids is energized. Torpedo 19 has a'conventional gyro controlledsynchro type steering servo 43u best lshown in FIG. 3 comprising a gyropickof synchro generator 42, which provides an error signal when thetorpedo deviates from a preset reference course and a synchro controltransformer 4dv which controls a rudder actuator 46 to maintain thetorpedo on the reference course in Yresponse to the error signal. Theratchet wheel of mechanism Mia drives the rotor of a synchrodifferential generator 48a inserted in the servo between generator d2and control transformer 44. In accordance with well known principles,rotation of the differential rotor modifies the electrical signal seenby the control transformer by an amount corresponding to the magnitudeof rotation. Accordingly, each step of angular rotation of mechanism 40aand in turn the rotor of the diiierential generator produces a simulatederror signal and the control transformer then operates the rudderactuator to cause the torpedo to turn to correct this simulated errorsignal and maintains the torpedo on new course with gyro control. Inother words, each step of angular rotation of mechanism 49a alters thegyroscopic controlled course by a small angular step. In similar manner,the depth steering servo 41h is of a synchro type responsive inoperation to a suitable depth sensing device which provides an errorsignal in accordance with deviation from a reference depth, and theoutput of relays 38C, 3&1 are fed to a like electromagnet and ratchetmechanism 4017 to effect incremental angular rotation in a differentialgenerator 48h similarly inserted in the depth servo to alter the depthcourse steering in incremental steps of depth. Preferably both theazimuth course and the depth servo are of the type providingproportional steering control to permit stable maneuvering at highspeeds.

If desired, transmission of a telemeter signal of the torpedo propellerrevolution count from torpedo 10 to control station l2 may be achievedbyprovision of a low impedance DC. source 5t) in the shipboard D.C.seawater ground return for the wire ld, and a contactor 52 mechanicallyconnected to the propeller shaft and arranged to short out a resistancein a D.C. seawater ground return for wire 1.3 in the torpedo. The DC.source causes flow of a D.C. current through the circuit through thesame wire conductor and seawater medium conducting path as Yused tocommunicate the A C. signals. Every time contactor 52 shorts out theresistance there is a momentary rise in voltage in the shipboard stationwhich operates a suitable counting and indicating device 54 in theremote station. This information is desirable for use in dead reckoningtechniques to track the torpedo position, which in turn permits higherquality guidance control. Y y Also, provision may be made to stop thetorpedo run from the control station by a stop switch 56 inserted inseries in the shipboard D.C. seawater ground return of wire lltiand astop relay 58 in the DC'. seawater ground return of wire l in thetorpedo, relay 58 having its contacts connected to the propulsion motorcontrol circuit.V Opening of switch 56 interrupts the flow of D.C.current through relay 58 shutting down the propulsion motor. Relay 58 isalso de-energized in event wire 1S breaks or develops substantialleakage and thereby provides a fail-safe shut down feature.

q FIG. 4 shows apparatus for controlling a torpedo from a shipboardstation differing from that of the device of FIG. 1 in that aconventional iilter circuit type frequency selective network 6G isemployed to separate the resultant A.C. signal, provided at the outputof the wire dispensing and communication circuit apparatus 32', into itscomponent signals. Apparatus titl has a series of four filter circuittype narrow band pass amplifiers 62a, 62b, etc., matched to theoscillators in transmitter unit 22'. The output of each band passamplifier is converted to a D.C. signal by suitable demodulators 64a,64b, 64C, 64d. In accordance with generally known principles, theaforesaid iilter circuit type apparatus is capable of operating athigher frequencies than the resonant reed relay apparatus of the deviceof FlG. l. Y K

FIG. 5 shows wire guided torpedo apparatus employing wire dispensing andcommunication circuit apparatus 32" like that of the device of FIG. 1.One portion of the available transmission band pass through theapparatus 32 is allocated as a communication channel for signals forcontrolling the torpedo from a shipboard station. Another portion isallocated as a communication channel for signals for telemeteringtorpedo performance data, including torpedo heading as measured by asuitable gyro device, torpedo depth as measured by a suitable pressuresensing device, and torpedo revolution count. Control of the torpedo isachieved by apparatus of the type hereinbefore described including acontrol signal transmitter 22 having its output signals Within thefrequency range allocated for the communication of control signals andfeeding its output to the shipboard end of apparatus 32 through asuitable band pass filter. The signals are communicated throughapparatus 32 to the torpedo where they are fed to a suitable band passamplifier and thence to a matching receiving unit 66, similar toreceivers 36 or 60, capable of separating the control signals.Telemetering is achieved by a matched set consisting of a suitabletelemetering transmitter 68 in the torpedo, capable of producing A.C.telemetering signals in accordance with the measured performance data,and a matchino telemetering receiver 70 at the shipboard station capableof separating the telemetering signals, of any suitable type known inthe art, both operating over the portion of the transmission band passallocated for telemetering. The output of transmitter 68 is fed to thetorpedo end of apparatus 32 through a suitable band pass filter.Apparatus 32" communicates the telemetering signals to its shipboard endwhere they are fed to receiver 70 through a suitable band passamplifier. Knowledge of such torpedo performance data at the ship isdesirable to permit accurate tracking of the torpedo by dead reckoningtechniques, which information in turn is used in solving the guidanceproblem.

The wire dispensing and communication circuit apparatus 32, 32' and 32"of the devices of FIGS. l, 4 and 5, respectively, has been found to beparticularly efficient for A.C. signalling. The attenuation lossexhibited by this apparatus is lower than that of a double conductorline of the same weight and bulk per unit length. When apparatus 32 isemployed with transmitting and receiving circuitry and over a distanceequal to the maximum required torpedo range, a practical transmissionband pass can be achieved extending through the frequency range requiredfor so-called audio frequency signalling techniques, which extends froma nominal zero frequency through 20,000 c.p.s. The upper practicableband pass cut-off for multi-frequency channel signalling techniques ashereinbefore disclosed occurs at approximately 30,000 c.p.s. where theslope, of the characteristic curve of attenuation loss versus frequency,increases to a magnitude producing undesired non-linear distortions.

It will be apparent that in controlling a torpedo at distances up tomaximum required torpedo range the number of coils 16 could sometimesdecrease considerably during a single torpedo run. Thus the inductiveirnpedance presented by the coils, which decreases with decrease innumber of turns, could therefore vary considerably during the run. Theseawater return portion of the transmission line formed by the uncoiledportion of the wire 18m that is immersed in the seawater medium has beenfound to exhibit a relative high distributed inductance per unit length,approching the inductance exhibited per unit coil length of coils 18a,18h. Such greater distributed inductance is desirable because itprovides more nearly uniform inductive loading of the transmission lineas the ratio of the length of wire in coils 18a, 18b to the length ofuncoiled Wire 18m changes during the torpedo run, thereby reducing thevariation in attenuation experienced during a run. Minimizing thevariation in attenuation during a run is particularly desired in thedevice of FlG. 5 where the frequency separation required betweencommunication channels of opposite direction, and therefore the signaltraflic handling capacity, is determined by the magnitude of suchvariation in attenuation. It is not fully understood why this relativelyhigh distributed inductance occurs, but it is believed that it is insome way connected with the fact that the combination of a single wireand seawater conducting paths form a configuration somewhat analogous tothat of a co-axial cable with the single wire representing the innerconductor, the insulation representing the dielectric separators, andthe seawater medium representing the outer conductor. The order ofmagnitude of the increased distributive inductance may be best envisagedby the fact that the distributed inductance has been found to beapproximately 10 times greater than that which would be exhibited by aco-axial cable with like inner conductor, a like di-electric separationbut having a metallic outer conductor having a conductivity equivalentto the conductivity of seawater. This property, of a high distributedinductance, very materially contributes to maintaining variation inattenuation of the system within desired limits.

Flooding dispenser housing Ma, Mb as heretofore described have beenfound to substantially reduce the attenuation losses exhibited by thetransmission line, and also obviates certain bothersome resonanceeffects. This margin of improved attenuation is especially significantin the device of FIG. 5 where it critically effects the frequencyseparation required between communication channels of oppositedirection, and therefore the signal trafiic handling capacity.

The apparatus shown in the drawings and above described are simpleexemplary forms of construction by which the desired results andmodifications thereof may be secured. For example, further segregationof communication channels may be obtained, such as by use of commutatingtechniques and the use of frequency modulation techniques.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

What is claimed is:

1. In multi-channel telecommunication apparatus for communicatingelectrical signals between two stations conl sisting of a torpedo and aremote telecommunication station, the combination, comprising;

(a) two or more sets of matched signal generation and ysignal detectionmeans employing a bandpass under 30,000 cycles per second, each set ofmatched means forming a separate communication channel and comprising asignal generator producing a distinctive signal disposed at one of saidstations, and signal detector means responsive to said distinctivesignal, only, disposed at the other station,

(b) the signal generators and signal detectors of the matching setsbeing coupled through a common signal transmission circuit comprising afirst electrical conduction path through an insulated single conductorWire and a second electrical conduction path through the saline oceanwater medium between the torpedo and the remote station,

(c) said insulated wire being of fixed length composed of a firstportion initially carried by the torpedo and forming a coil which isprogressively dispensed into the ocean medium between the torpedo andthe remote station under movement of the torpedo, whereby aprogressively lengthening uncoiled portion of Wire is disposed in theocean medium between said stations,

(d) said uncoiled portion of the wire and the water medium effectivelyforming a co-axial transmission line in which the ocean water mediumsurrounds the conductor of the wire and the insulation of the wiredisposed between the ocean water and the conductor, said insulatedconductor wire having an outer protective sheath of insulation and anintermediate sheath of insulation between the outer sheath and theconductor, said intermediate sheath being of substantial thickness andmade of a material having a lower value of di-electric constant than theinsulation material of the protective sheath to lower the shuntdistributed capacity of the co-axial transmission line, whereby theocean water medium surrounding the 7 wire cooperates with same toprovide a co-axial transmission line configuration which exhibitssubstantial distributed inductance, to thereby compensate for variationof attenuation due to progressive uncoiling of the coiled portion of thewire,

(e) said first coiled portion of the wire carried by the torpedo in arst compartment flooded with said saline water medium, said first coiledportion forming a first multi-layer coil of annular shape having anaxial aperture extending between its ends, said annular coil beingsupported in substantially spaced relation to the walls of thecompartment, whereby the coil is substantially surrounded by and itsaxial aperture is filled with said saline water medium to obviateundesired gross non-linearities in the bandpass of the coupling circuit.

2. Apparatus in accordance with claim 1, wherein (f) the outerprotective sheath of insulation is made of nylon and the intermediatesheath of insulation is made of polyethylene.

3. Apparatus in accordance with claim 1,

(g) said first annular coil being of the type in which the wire endadapted for dispensing is disposed adjacent said axial aperture and maybe unraveled therefrom in response to a nominal axial pulling force, and

(h) a wire dispensing tube having its receiving end disposed adjacentone endl of the annular coil and aligned along its axis, and having itsdispensing end projecting from the hull of the torpedo.

4. Apparatus in accordance with claim 1, wherein (i) said signalgenerator and said signal detector means of each matched set comprisesan oscillator having a predetermined frequency of oscillation and afrequency selective circuit tuned to said predetermined frequency,respectively.

5. Apparatus in accordance with claim 4, wherein (j) the signalgenerator of a iirst'matched set is disposed at one of said stations andthe signal generator of a second set is disposed at the other station.

6. ApparatusV in accordance with claim 1, wherein said remote station isalso carried by a movable vehicle,

(k) said length of insulated wire being also composed of a secondportion initially carried by the movable vehicle and forming a coilwhich is progressively dispensed into the ocean medium between thetorpedo and the remote station under movement of the vehicle,

(l) said second coiled portion of the wire carried by the movablevehicle in a second compartment flooded with said saline water medium,said second coiled portion forming a second multidayer coil of annularshape having an axial aperture extending between its ends, said annularcoil being supported in substantially spaced relationship to the wallsof the compartment.

7. In combination with a torpedo, multi-channel telecommunicationapparatus, employing a predetermined bandpass under 30,000 cycles persecond, for communicating electrical signals between the torpedo and aremote station, said multi-channel telecommunication apparatus being ofa type normally provided with a radio-type signal transmission circuithaving essentially xed attenuation characteristics and having linearlyoperating characteristics over said bandpass, whereby the dynamic rangefor reliable operation of multi-channel apparatus is not exceeded, butsaid telecommunication apparatus having insuflicient dynamic range forreliable operation in the presence of non-linear distortions in saidbandpass, ythe improvements comprising;

(a) a wire line transmission circuit of the type which is progressivelydispensed from a coil, said wire line inter-connecting the torpedo andthe remote station in lieu of the radio-type signal transmissioncircuit,

said wire line transmission circuit comprising a fixed length of singleconductor insulated wire-forming a first electrical conduction pathbetween the torpedo and the remote station, said xed length of wireinitially forming a coil carried by the torpedo and which isprogressively dispensed into the ocean medium between the torpedo andthe remote station under movement of the torpedo,

Y (b) said wire line transmission circuit being adapted to form a secondelectrical conduction path through the saline ocean water medium betweenthe torpedo and the remote station,

(c) said wire which is dispensed in the ocean medium and the watermedium eiectively forming a co-axial transmission line in which theocean water medium surrounds the conductor and the insulation isdisposed between the ocean water and the conductor, said insulatorcomprising a sheath of insulation including a substantial thickness oflow di-electric insulation material, the construction of the sheath ofinsulation being such as to lower the shunt distributed capacity of theco-axial transmission line, whereby the ocean water medium surroundingthe wire cooperates with same to provide a co-axial transmission lineconfiguration which exhibits substantial distributed inductance, tothereby compensate for variation of attenuation due to progressiveuncoiling of said coiled portion of the wire and thereby minimizedistortion of bandpass,

(d) means carried by the torpedo for flooding said coil carried by thetorpedo to obviate undesired resonance-like non-linearities of bandpassexhibited by the coil.

8. Apparatus in accordance with claim 7, wherein (e) the value ofdi-electric constant of the low dielectric material in the insulationsheath is under four.

9. Dispensable wire apparatus for providing an electrical conductionpath between two stations consisting of a torpedo and a torpedo remotetelecommunication station on a maneuverable vehicle, comprising,

(a) a single continuous insulated electric conductor having a iirstportion formed into a coil and carried by the torpedo, a second portionformed'into a coil and carried by the maneuverable vehicle, and amid-portion joining said i'lrst and second portions disposed in thewater between the torpedo and the maneuverable vehicle,

(b) said coiled portions forming a multi-layer coil of annular shapehaving an axial core aperture extending therethrough and of the type inwhich the end of the coil appears at innermost layer adjacent the axialaperture joined to the mid-portion and may be unraveled therefrom inresponse to a nominal axial pulling force,

(c) whereby the wire is dispensed from the respective coils into thewater medium under movement of either the torpedo or of the Vehiclerelative to the midportion of the wire with said midportion remainingessentially stationary with reference to the water medium andexperiencing no more than nominal tension forces therein.

References Cited in the le of this patent UNITED STATES PATENTS 619,023Litchfield Feb. 7, 1899 719,405 Wilson Ian. 27, 1903 1,117,943 HelfrichNov. 17, 1914 1,319,678 Hammond Oct. 2l, 1919 1,418,789 Hammond June 6,1922 2,050,665 Matthews et al Aug. l1, 1936 2,784,393 Schultheis Mar. 5,1957 2,984,783 Singer May 16, 1961 2,996,027 Cooke Aug. 15, 1961

1. IN MULTI-CHANNEL TELECOMMUNICATION APPARATUS FOR COMMUNICATINGELECTRICAL SIGNALS BETWEEN TWO STATIONS CONSISTING OF A TORPEDO AND AREMOTE TELECOMMUNICATION STATION, THE COMBINATION, COMPRISING; (A) TWOOR MORE SETS OF MATCHED SIGNAL GENERATION AND SIGNAL DETECTION MEANSEMPLOYING A BANDPASS UNDER 30,000 CYCLES PER SECOND, EACH SET OF MATCHEDMEANS FORMING A SEPARATE COMMUNICATION CHANNEL AND COMPRISING A SIGNALGENERATOR PRODUCING A DISTINCTIVE SIGNAL DISPOSED AT ONE OF SAIDSTATIONS, AND SIGNAL DETECTOR MEANS RESPONSIVE TO SAID DISTINCTIVESIGNAL, ONLY, DISPOSED AT THE OTHER STATION, (B) THE SIGNAL GENERATORSAND SIGNAL DETECTORS OF THE MATCHING SETS BEING COUPLED THROUGH A COMMONSIGNAL TRANSMISSION CIRCUIT COMPRISING A FIRST ELECTRICAL CONDUCTIONPATH THROUGH AN INSULATED SINGLE CONDUCTOR WIRE AND A SECOND ELECTRICALCONDUCTION PATH THROUGH THE SALINE OCEAN WATER MEDIUM BETWEEN THETORPEDO AND THE REMOTE STATION, (C) SAID INSULATED WIRE BEING OF FIXEDLENGTH COMPOSED OF A FIRST PORTION INITIALLY CARRIED BY THE TORPEDO ANDFORMING A COIL WHICH IS PROGRESSIVELY DISPENSED INTO THE OCEAN MEDIUMBETWEEN THE TORPEDO AND THE REMOTE STATION UNDER MOVEMENT OF THETORPEDO, WHEREBY A PROGRESSIVELY LENGTHENING UNCOILED PORTION OF WIRE ISDISPOSED IN THE OCEAN MEDIUM BETWEEN SAID STATIONS, (D) SAID UNCOILEDPORTION OF THE WIRE AND THE WATER MEDIUM EFFECTIVELY FORMING A CO-AXIALTRANSMISSION LINE IN WHICH THE OCEAN WATER MEDIUM SURROUNDS THECONDUCTOR OF THE WIRE AND THE INSULATION OF THE WIRE DISPOSED BETWEENTHE OCEAN WATER AND THE CONDUCTOR, SAID INSULATED CONDUCTOR WIRE HAVINGAN OUTER PROTECTIVE SHEATH OF INSULATION AND AN INTERMEDIATE SHEATH OFINSULATION BETWEEN THE OUTER SHEATH AND THE CONDUCTOR, SAID INTERMEDIATESHEATH BEING OF SUBSTANTIAL THICKNESS AND MADE OF A MATERIAL HAVING ALOWER VALUE OF DI-ELECTRIC CONSTANT THAN THE INSULATION MATERIAL OF THEPROTECTIVE SHEATH TO LOWER THE SHUNT DISTRIBUTED CAPACITY OF THECO-AXIAL TRANSMISSION LINE, WHEREBY THE OCEAN WATER MEDIUM SURROUNDINGTHE WIRE COOPERATES WITH SAME TO PROVIDE A CO-AXIAL TRANSMISSION LINECONFIGURATION WHICH EXHIBITS SUBSTANTIAL DISTRIBUTED INDUCTANCE, TOTHEREBY COMPENSATE FOR VARIATION OF ATTENUATION DUE TO PROGRESSIVEUNCOILING OF THE COILED PORTION OF THE WIRE, (E) SAID FIRST COILEDPORTION OF THE WIRE CARRIED BY THE TORPEDO IN A FIRST COMPARTMENTFLOODED WITH SAID SALINE WATER MEDIUM, SAID FIRST COILED PORTION FORMINGA FIRST MULTI-LAYER COIL OF ANNULAR SHAPE HAVING AN AXIAL APERTUREEXTENDING BETWEEN ITS ENDS, SAID ANNULAR COIL BEING SUPPORTED INSUBSTANTIALLY SPACED RELATION TO THE WALLS OF THE COMPARTMENT, WHEREBYTHE COIL IS SUBSTANTIALLY SURROUNDED BY AND ITS AXIAL APERTURE IS FILLEDWITH SAID SALINE WATER MEDIUM TO OBVIATE UNDESIRED GROSS NON-LINEARITIESIN THE BANDPASS OF THE COUPLING CIRCUIT.